Precast concrete is a form of construction, where concrete is cast in a reusable mold or “form” which is then cured in a controlled environment, transported to the construction site and lifted into place. In contrast, standard concrete is poured into site specific forms and cured on site. Precast stone is distinguished from precast concrete by using a fine aggregate in the mixture so the final product approaches the appearance of naturally occurring rock or stone.
By producing precast concrete in a controlled environment (typically referred to as a precast plant), the precast concrete is afforded the opportunity to properly cure and to be closely monitored by plant employees. Many states across the United States require a precast plant to be certified (either by NPCA or PCI) for a precast producer to supply their product to a construction site sponsored by State and Federal Departments of Transportation (DOTs).
Ancient Roman builders made use of concrete and soon poured the material into molds to build their complex network of aqueducts, culverts and tunnels. Modern uses for precast technology include a variety of architectural and structural applications featuring parts of or an entire building system. Precast architectural panels are also used to clad all or part of a building facade, free-standing walls used for landscaping, soundproofing and security walls. Storm water drainage, water and sewage pipes and tunnels make use of precast concrete units. The advantages of using precast concrete is the increased quality of the material, when formed in controlled conditions, and the reduced cost of constructing large forms used with concrete poured on site.
There are many different types of precast concrete forming systems for architectural applications, differing in size, function and cost.